The thing you're not mentioning is that these doctors don't live in Cuba. They live in capitalist countries in which the government doesn't (even try to) provide X, Y, and Z.

Sure, the doctors got a free education, and that's worth a lot. But at some point they'll have paid off the value of that education and after that point, they're still being taxed at some very high rate and they're seeing no benefit from those taxes because they live in Brazil. Seems like exploitation to me.